Biological samples are routinely examined for the presence of abnormal organisms or cells, such as ova, parasites, microorganisms, and inflammatory cells by conventional light microscopy of smear preparations. Visual detection of such materials in smears is hindered by the presence of masking particulate or other matter interspersed between cells. Additionally, standard smear preparations utilize only a minute fraction of the sample since the smears must be thin enough to allow the passage of light. Examination of multiple smears to compensate for these drawbacks is impractical in the busy hospital laboratory. Consequently, the sensitivity of disease detection is suboptimal using the smear methodology.
Ova and parasites present in stool may be concentrated by employing filtration techniques whereby the sample specimen is made relatively dense so that the ova, and/or parasites, and/or cysts will float on the surface of the sample. This technique however does not permit the visualization of the target organisms or ova in the concentrated specimen. The target layer must be aspirated or transferred to a slide for examination, whereupon a large number of the target organisms or cysts are lost.
Cytologic evaluation of tissue cells in smears derived from biological fluids and tissues for the purpose of diagnosing cancer is an integral part of the practice of medicine. These examinations are; however, typically performed on less than 5% of the cells sampled due to the aforesaid requirement that smears be thin. Furthermore, as noted, tissue cells in these preparations are often obscured from view by contaminating blood cells and debris.
Cytologic evaluation of tissue cells in feces for the diagnosis of colon cancer has not been used to any significant extent. In fact, the index of a recently published authoritative cytology textbook (Comprehensive Cytopathology, Marluce Bibbo; ed. W. B. Saunders Company, 1991) contains no references to either stool or feces evaluation. This deficit may be explained by the paucity of tissue cells in the standard stool smear, and the abundance of obscuring debris. Consequently, cytologic examination of stool by the smear protocol is virtually useless as part of a cancer screening.
Medical diagnostics of stool and other biological samples would be greatly improved by a technique which does not depend on the use of a very limited amount of sample material, such as is inherent in the examination of specimen smears. The reason for this is that when one is able to use a larger specimen sample in the screening or examination, the odds are increased that target materials will be included in the sample and identified.
U.S. Pat. No. 4,190,328, granted Feb. 26, 1980, to R. A. Levine et al describes a process for the detection of blood-borne parasites in a sample of centrifuged anticoagulated whole blood. The blood sample is mixed with a stain and then centrifuged in a tube containing a volume-restricting float. Target parasites which may be in the blood sample are highlighted by the stain and trapped between the float and the bore of the tube where they can be visually observed under appropriate magnification.
U.S. Pat. No. 4,717,660, granted Jan. 5, 1988, to T. H. Schulte discloses a procedure for detecting bacteria in an anticoagulated blood sample, and for assessing phagocytic activity in the blood sample. The blood sample is mixed with a stain that will highlight the bacteria, and the mixture is centrifuged in a tube containing a volume-restricting float. The buffy coat in the centrifuged blood sample settles into the restricted space between the tube bore and float, and the cell bands in the buffy coat are thereby physically elongated. Any bacteria in the blood will be differentially stained and will be located in one of the buffy coat cell bands, where such bacteria can be observed under appropriate magnification.
The aforesaid patented procedures are restricted to diagnosing blood samples, and do not suggest any diagnostic procedures wherein non-fluid biological samples, or fluid biological samples, other than blood, can be analysed quickly and dependably for target malady-specific materials.